![(Alt Text: Joy apologizing formally [Shimaimashita] vs. Joy saying 'Oops' playfully [Chaimashita])](https://jplt-dialogplus.com/wp-content/uploads/2025/12/ChatGPT-Image-Feb-15-2026-02_54_12-PM.png)
(Joy apologizing formally [Shimaimashita] vs. Joy saying ‘Oops’ playfully [Chaimashita])
“I forgot!” (Wasurete shimaimashita)
“I forgot!” (Wasure chaimashita)
Both mean “I accidentally did it (and I regret it).” However, one is suitable for a CEO, and the other is for your best friend. “~Chaimashita” is the spoken, casual version (contraction). Let’s master the switch with Joy and Ken!
🗣 Conversation Scene
Joy makes mistakes in two different situations.
すみません！資料（しりょう）を忘（わす）れて しまいました。
(I’m sorry! I [accidentally/regrettably] forgot the documents.)
ごめん！ケンさんのプリン、食（た）べ ちゃいました。
(Sorry! I [oops] ate your pudding.)
💡 Explanation
Formal Speech vs. Spoken Sound Change
1. 〜て しまいました (~te shimaimashita)
Formal / Polite
This is the standard grammar form. It expresses regret (“I didn’t mean to, but it happened”) or completion (“I finished it all”). Use this with bosses, strangers, or in writing.
- 電車（でんしゃ）で 寝（ね）て しまいました。
(I fell asleep on the train [by accident/regret].)
2. 〜ちゃいました (~chaimashita)
Casual / Spoken
This is a contraction (shortened form) of “~te shimaimashita”. It sounds friendly, soft, or sometimes childish.
*Grammar Rule: “~te shimau” becomes “~chau”.
- 電車で 寝（ね）ちゃいました。
(I fell asleep on the train [Oops!].)
- Verbs ending in TE (Tabete) → Cha (Tabechau)
- Verbs ending in DE (Nonde) → Ja (Nonjau)
Ex: 飲んでしまいました (Nonde shimaimashita) → 飲んじゃいました (Nonjaimashita).
📊 Comparison Table
🚧 Joy’s Mistake
(Joy broke a very expensive plate at work)
❌ Wrong: 社長（しゃちょう）、お皿を 割（わ）っちゃいました。
(Tone: “Oopsie! I broke the plate.” This sounds too light and insincere for a big mistake at work.)
✅ Right: 社長、お皿を 割ってしまいました。
(Tone: “I deeply regret that I broke the plate.” This shows proper remorse.)
🔥 Practice Quiz
Tap to check the answer!
